1. Field of the Invention
The present invention relates generally to integrated circuits, and more specifically, the present invention relates to integrated circuits that are controllers for switching power supplies.
2. Background Information
A large class of switching power supplies operates with a fixed switching frequency. It is often desirable to know that the switching frequency will not deviate by more than a specified amount from a nominal value during normal operation of the power supply. Such knowledge is very useful to designers because it allows them to select optimum components for the power supply and for the system that must operate with it.
Designers choose a switching frequency that is suitable for the particular application. The selection of frequency depends typically on the amount of power to be processed and the topology of the power converter. Various other parameters and specifications that are important to the use of the power supply also influence the selection of its switching frequency.
The controllers for modern switching power supplies are typically integrated circuits. Some integrated circuit controllers have only one fixed switching frequency, whereas others offer the designer a choice of two or more fixed switching frequencies. The controllers that have options for more than one fixed frequency typically allow the designer to select the desired frequency by way of a particular connection of terminals on the integrated circuit.